Telephone system



D. F. WHITING. TELEPHONE SYSTEM.

APPucATloN FILED DEc.28.191s.

l1,327,185. Patented Jan. 6,1920.

UNITED r DONALD F. WHITING, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

To all whom t may Concern:

Be it known that I, DONALD F. WHITING, a citizen of the United States, residing at New York, in the county'of Bronx, State of New York,.have invented certain new and useful Improvements `in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systems and more particularly to such systems lemploying long t ansinission lines over which both telephonic and signaling currents may be transmitted.

In such systems the signaling current required for operating the signal control apparatus associated with the switchboard ends of the transmission line is usually of low frequency and is not suitablefor transmission over long transmission lines. It is customary, therefore, to associate with the line apparatus which is responsive to low frequency signaling currents transmitted from the switchboard end of the line for connecting higher frequency signaling currents with the line for transmission thereover. Apparatus responsive to the higher frequencysignaling currents is also provided intermediate the ends of the line for connecting with the switchboard end low frequency signaling currents suitable forv operating the signaling apparatus locatedat the switchboard. Y

The object of this inventionis to provide improved signaling means for systems of this character.

In attaining the object of the present invention, therefore, the apparatus responsive to signaling currents transmitted over the line may be associated therewith through an amplifier whose connection -with the line is through means resonant to the signaling currents transmitted over the l'ine.

For a more complete understanding of this invention, reference should be had to the following description, considered'in connection withthe accompanying drawing, which illustrates the inventionembodied in -a fourwire transmission system of which .only so much is shown as is necessary for a proper understanding of the present invention.

complete four-wire transmission system, with which the arrangements of the present in- Specification of Letters Patent.

the repeating coil.

Patented J an. 6, 1920.

Application filed December 28, 1918. Serial No. 268,756.

' terminating Circuit L3 extending from the junction station to terminating apparatus (not shown) at a switchboard. The termi-.

nating circuit L3 is associated with the outgoing circuit L2 through a repeating coil comprising primary windings 5, 5 and secondary windings 6, 6. The incoming circuit L1 is connected with the terminating circuit L3 through the windings of an auto-transformer 7, bridged across the mid-points ofA the primary windings 5, 5 of the repeating coil. The incoming circuit L1 and the terminating circuit L3 are of different impedances, and the auto-transformer 7 serves to minimize reflection losses resulting from the transmission of telephonie currents from the incoming circuit L1 to the terminating circuit L3. For the purpose of balancing the terminating circuit'L3 with respect to currents incoming over the incoming circuit L1, there'is provided an artificial balancing line L4 connected in circuit with the primary windings 5, 5 of the repeating coil.

In order that signaling current of the proper frequency (approximately 133 cycle) for propagation over the transmission line may be connected with the outgoing circuit L2 when low frequency signaling current (approximately 16 cycle) is impressed upon the terminating circuit/ L3 at the switchboard end thereof, there is provided at the junction station a ringing response relay 8 connected in series, with a condenser 9 and in bridge of the terminating circuit L3. For proper balancing, the relay 8v and its associated condenser 9 are connected across the mid-points of the primary windings 5, 5 of This ringing response relay 8 responds to 16 cycle signaling current, and through a slow release relay 10 controlsv the connection of 133 cycle signaling current with the outgoing circuit L2.

I n order that low frequency signaling current for operating signal control apparatus at-the switchboard maybe connected with the terminating circuit L3 when the higher frequency signaling current is transmitted over the incoming circuit L1, there is provided at the junction station a relay 11 responsive to 133 cycle signaling current incoming over the circuit L1. This relay 11 controls through a slow-operating and slow releasing relay 12 and a rii'lging relay 13, the connection of 16 cycle signaling current with the terminating circuit L3. The relay 11 is connected in the output circuit of an amplifier 11, whose input circuit is connected in series with the secondary winding of an input repeating coil 15. The primary winding of this input coil 15 is connected in parallel with a condenser 17. This condenser 17 is connected between the middle windings of the auto-transforn'ier 7 and serves to provide a path of low iinpedanceto talking currents. The' condenser 17 is also of higher impedance to signaling current of 133 cycles and coperates with the primary winding of the input coil 15 to form a closed circuit resonant tosignaling current 133 cycles. Therefore, when 133 cycle signalling current is impressed across the terminals of the condenser 17, local oscillatory currents are set up in the closed resonating circuit. These local oscillatory currents, which are of much greater magnitude than the currents incoming over the line section L1, in flowing through the primary winding of the input coil 15, induce potentials in the secondary winding of this coil. These induced potentials are impressed upon the input electrodes of the amplifier 11. Due to these oscillatory currents of great magnitude, the closed resonating circuit offers an effective impedance to signaling currents of 133 cycles commensurate with thev impedance offered to these currents by the autotransforiner and the incoming line section L1, thereby minimizing the effect of the impedance of the auto-transformer to such cuirents. Condensers 22 and 23, through which the auto-transformer 7 is connected with the mid-points of the primary windings, 5, 5 are of 4such capacity as to present a very high impedance to signaling currents but a very low .impedance to talking currents.r 1t will be understood, therefore, that the shunt path about the ringing response relay 8 is of high impedance to signaling currents to which this relay is responsive. A condenser 18 provided in series with the windings of the relay 11, prevents the flow of direct current therethrough and coperates with the inductance of the relay to tune the output circuit to 133 cycle signaling current.

If talking currents be transmitted from the switchboard end of the terminating circuit L, these currents are induced through the windings of a repeating coil into the outgoing circuit L2, while talking currents transmitted over .the incoming circuit L1 traverse the windings of the auto-transformer T and are induced into the terminating circuit L3.

If signaling current of 133 cycles be transmitted to the junction station over the incoming circuit L1, these impulses are 'repeated through the windings of the input `coil 15 into the input circuit of the amplifier 11, which amplifies them and transmits them into the output circuit inwhich the relay 11 is connected. upon responds to such amplified signaling current incoming over the incoming circuit L1,.and opens the normally closed energiz ing circuit of the relay 12. This relay, in releasing its armature, completes an energizing circuit causing the operation of ringing'relay 13. The operation of this ringing relay 13 connects the source of signaling current 20 with the terminating circuit L3.

Low frequency signaling current incoming to the junction station over the terminating circuit L3 from the switchboard end thereof causes the operation of ringing response'relay 8, this relay, through the cooperation of the associated condenser 9, being tuned to respond to signaling currents of this frequency. The operation ot' this ringing response relay 8, causes the operation'of the slow release ringing relay 10, which connects the source of signaling current 21 with the outgoing circuit L2. The operation of this relay 10 also closes a contact which is in multiple with the norkmally closed Contact of the relay 11. This is to insure that relay 12 will not release should the ringing response relay 11 accidentally respond to the 16 cycle signaling current incoming to the junction station over the terminating circuit L3.

Thile the present invention has been shown in connection with the terminating end of a four-wire transmission system, it will be apparent that it is equally applicable to a two-wire system in which signaling' currents of one frequency are transmitted over one line section for operating switching apparatus, which connectssignaling current of another character with the succeeding line section.

What is claimed is:

1. In a telephone system, in combination, a transmission line, an amplifier for amplifying signaling currents transmitted over one section of the line, a parallel circuit comprising a condenser and an impedance resonant to signaling .current connecting the amplifier with the one line section, a separate source of signaling current, and a relay responsive toamplified signaling currents for controlling kthe connection of the separate source with another section of the line.

2. In a telephone system, in combination, a transmission line, an amplifier for amplifying signaling currents transmitted over The relay 11 therenaam se therewith tlie amplifier, a separate source of signaling current, and a relay responsive to amplified signaling currents for controlling the connection of the separate source with another section of the line.

B. In a telephone system, in combination,

a transmission line, an amplifier for amplifying signaling currents transmitted over one section of the line, a condenser connected with the transmission line, a transformer having its primary winding connected in a closed circuit with the condenser and its secondary winding connected with the amplifier, a separate source of signaling current, and a relay responsive to amplified signaling currents for controlling the connection of the separate source with another section of the line.

4. In a telephone system, in combination, a transmission line, an amplifier for amplifying signaling currents transmitted over one section of the line, a condenser, a transformer having its primary winding associated with the condenser to form -a closed circuit and connected in bridge of the one line section and resonant to "signaling currents transmitted thereover, vthe secondary 4winding being connected with the amplifier, a separate source of signaling current, and a relay responsive to amplified signaling current for controlling the connection of the separate source with another section of the line.

5. In a telephone system, in comb-ination, two sections of a transmission line of different impedances over which talking and signaling currents are transmitted, means joining the sections for minimizingv reflection losses resultingv fromlthe transmission of talking currents from one section to the other, an amplifier for amplifying signaling currents transmitted over one line section, means resonant to signaling current coperating with the reflection loss minimizing means for associating the amplifier with the one line section, a separate source of signaling current, and a relay responsive to amplified signaling currents for controlling the connection of the separate source with the second line section. y

6. In a telephone system, in combination,l

ing current coper'ating with the autotransformer for associating the amplifier with the one line section, a separate source of signaling current and a relay responsive to amplified signaling current for controlling the connection of the separate source with the second line section.

7. In a telephone system, in combination, two sections of a transmission line of different impedances over which talking and signaling currents are transmitted, an autotransformer joining the sections for minimizing refiection losses resulting from the transmission of talking current from oneV section tothe other, an amplifier for amplifying signaling currents of one character transmitted over one line section, a condenser connected between' the windings of the autotransformer, a repeating coil having a primary winding connected in a closed 'circuit with the condenser and its secondary winding connected with the amplifier, a separate source of signaling current, and a relay responsive to amplified signaling current for controlling the connection of the separate source with the second line section.

S. In a telephone system, in combination, two sections of a transmission'line of different impedances over which talking and signaling currents are transmitted, means joining the sections for minimizing reflection losses resulting fromk the transmission of talking currents from one section to the other, an electroresponsive device responsive to signaling current 4transmitted over one line section, means'resonant to signaling current coperating with the reflection loss minimizing means for associating the electroresponsive device with the one line section, a separate source of signaling current, and a switching relay operating upon the response of the electroresponsive device to connect the separate source with the other line section.

9. In a telephone system, in combination, two sections of a transmission line-of different impedances over whichtalking and signalin currents, are transmitted, an autotransformer joining the sections for minimizing reflection losses resulting from the transmission of talking currents from one section to the other, a condenser connected between the windings of the autotransformer, an electroresponsive device responsive to signaling current transmitted over one line section, a transformer having its primary winding associated with the condenser to form a closed circuit resonant to the signaling currents transmitted over the one line section and having its secondary winding associated with the electroresponsive device, and a separate source of signaling current connected with the other line section upon the response of the electroresponsive device.

l0. In a telephone system, in combination,

two sections of a transmission line of different mpedances over which talking and signaling currents are transmitted, ineans joining the sections for minin'iizing reflection losses resulting from the transmission of talking' currents from one section to the other, an electroresponsive device responsive to signaling` current of one character transmitted over one line section for controlling 10 the connection of signaling current of a different character with the other line section, and means resonant to signaling current transmitted over tlie one line section and cooperating with the reflection` loss minimizing ineans for associating the electroresponsil device With the one line section.

In Witness whereof I hereunto subscribe iny naine this 27th day of Decenibelg A. D. 1918.

DONALD F. WHITING. 

